Forthcoming Breakthroughs

Many new technologies are needed to make CVCs possible, as well as effective. Major research efforts must be made to develop and apply theories to present-day cells.

The most important advancement that must be made involves artificial chlorophyll. Scientists currently know the molecular configuration of the substance (C55H72MgN4O5 and C55H70MgN4O6)6 and its properties. With developments in the field of nanotechnology, it may be possible in the future to engineer substances at the molecular level cheaply and efficiently. Scientists could extract the chlorophyll from plants grown in special labs and alter it for application in CVCs. Furthermore, the artificial chlorophyll need not be organic at all. Dyes composed of complicated transition metal complexes that strongly absorb sunlight can act as the chlorophyll. To date, the complexes of the cis-NCS2 bis (4,4'-dicarboxy-2,2'-bipyridine) ruthenium (II) family are best23, but in the future, osmium (II) or rhenium (I) complexes, or metal cyanides will exhibit even better absorption spectrums and life spans, as predicted by present scientists24. These materials have promising capabilities in light absorption and stable excited states.

With research into the structures and behaviour of reaction centres and antennae, the number of reaction centres can be pre-determined upon chlorophyll synthesis; that is, more will be created for cells exposed to high-concentration light and fewer for those exposed to low-concentration light. It may even be possible to create “smart” pigments that act as antenna or reaction centres, depending on light conditions. One method of doing this may involve modifying the light-harvesting protein complexes that the pigment molecules are bound to, since they guide transferred energy to the reaction centre. These proteins can be altered to determine assembly structure using advanced nanoprobes with chemical manipulators connected to the proteins (Fig. 4). In this way, not only will energy conversion be more efficient, but also if one reaction centre deteriorates, the entire assembly is not rendered useless, as another will take its place.

Figure 4: Assembly modification of the CVC.

To make electron flow unidirectional, sophisticated “Iads” (insulator-acceptor-devices, modified from a current concept) may be attached to the conducting molecular chains. These devices will be rigid lengthened molecules that consist of an insulator molecule attached to an electron-accepting molecule. Electrons that enter the molecular chain must travel through the insulator molecule, which acts as a tunnel junction to the acceptor molecule. The Iad prevents electron movement in the opposite direction. Future Iads will compose of short insulating molecular chains such as linear polyalkyl -(CH2)x-26, and other synthesized polymers.

With regards to production, improved nanotechnology will allow the molecular analogue of a wire grid to be produced on the film. Using nano-sized cutting lasers, synthetic chlorophyll can be separated into molecular “wires.” The conductive molecular chains can be made into a liquid with Iads dissolved within, and poured into the spaces between spaces on the film. High pressure will force the liquid into the depressions, while electric fields will align the Iads into the same direction, and the solution will then be solidified. Special machines capable of delicate procedures must be designed for CVC production.

For CVCs to be practical they must be made to last many years. Durability of chlorophyll will be increased such that it can withstand ongoing cycles of oxidation and reduction. Metallic-based molecules with strong molecular forces will likely be used due to stability. Nevertheless, organic molecules may also be used, with increased strength from chemical dopants and modification of molecular bonds.